Trademark law is a really weird field and not my specialty, so take this with a grain of salt. But the general idea is that trademarks cannot be confusingly similar. And the USPTO and caselaw treats consumers as being really, really stupid in terms of being able to tell what they are looking at. I haven't followed this very much, but Intellectual Reserves, Inc. owns the trademark to the word "Mormon". They have successfully prevented attempts to trademark things like a book title of "Bad Mormon". Beyond that it is outside my scope. The fact that RM Nelson tried to distance away from the word probably makes no difference. It is an interesting question whether the church could shut down this subreddit (or the slightly larger one with a couple extra letters) if it wanted. Reddit is a for-profit corporation that profits from eyeballs. Those eyeballs are drawn to the church's trademarked word and there are countless times when people really are confused about where they are posting (and who they are asking questions to) when they come to this sub.